Caterpillar Tractor Co.

Caterpillar Inc.

James D Rinaldo

Gordon W Johnson

Maurice F Franz

Thomas J Bubula

Robert M Vize

Jose M Salazar-Vior

Randall L Mooberry

Jeffery A Crosser

Cushioned swing circuits sometimes have a restricted passage between the motor conduits to allow the implement controlled by the swing circuit to coast to a stop. However, opening and closing of the restricted passage was manually controlled, thereby requiring an additional manipulative step by the operator. The present cushioned swing circuit includes a cushion valve moveable to an open position to establish communication through vent line means when a pressure differential greater than a predetermined level is generated in one of the motor conduits connecting a directional control valve to a hydraulic motor. The cushion valve is retained in the open position for a predetermined limited time after the pressure differential drops below the predetermined level so that the inertia generated pressure in the circuit is dissipated through the vent line means. At the end of the predetermined limited time, the cushion valve is moved to the closed position blocking communication through the vent line means whereupon the circuit is hydraulically locked. The cushion valve is moved between the opened and closed positions automatically and requires no additional effort by the operator.

Cushioned swing circuit

Transmission filler assembly

A drive train includes a hydrostatic transmission unit and a multiple speed range transmission unit arranged in series between a prime mover and a primary output shaft, variable displacement and torque transmitting capacity of the hydrostatic transmission unit being adjusted by hydraulic controls including a speed control valve for developing a differential pressure signal proportional to a desired rate of operation, a modulating valve for regulating the differential pressure signal corresponding to accelerating and decelerating operation of the transmission, a directional control valve for determining the direction of operation of the hydrostatic transmission unit, and a range selector valve for shifting the operating speed range of the multiple speed range transmission as the hydrostatic transmission approaches a limit of displacement, the displacement of the hydrostatic transmission being automatically reset in response to shifting of the multiple speed range transmission. Operating speed limits are automatically established for the drive train by an override speed control valve which manually adjusts the differential pressure signal for reduced torque transmission through the drive train when the prime mover is operating below a minimum speed. A speed limiting control valve responds to operation of the prime mover above a maximum selected speed for automatically applying a brake within the drive train in order to supplement dynamic braking capacity of the transmission unit, the speed limiting control valve including means producing a feedback signal for resisting manual operation of the override speed control valve in proportion to engagement of the brake within the drive train.

Controls for combined hydrostatic and multiple speed range transmission

A hydrostatic transmission has a pair of variable displacement overcenter hydraulic pumps and first and second rotary servo valves. Each servo valve has a housing connected to the respective pump and a valve spool rotatably positioned within the housing for controlling the output displacement of the respective pump. A mounting plate extends between and is releasably connected to the housings of the first and second servo valves. A first device is connected to the valve spool of the first servo valve for selectively rotating said first servo valve spool, said first device being mounted on said mounting plate adjacent said first servo valve spool. A second device is connected to the valve spool of the second servo valve for selectively rotating the second servo valve spool, said second device being mounted on said mounting plate adjacent said second servo valve spool. A third device interconnects the first and second devices for causing simultaneous rotation of said valve spools in response to a single input signal to one of the first and second devices.

Modular control linkage assembly for a hydrostatic transmission

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Joliet, IL, United States of America

James D Rinaldo